Balanced slide-valve.



No. 682,92I.

(un mmol.)

H. D. & C. L. DUNBAR.'

BALANCE!) SLIDE VALVE.

".ulmw mi (Application am my 1, 1901.)

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Patented Sept, I7, |90l.

2 Sheets-Sheet I.

No. 682,921. Patented Sept. I7, I90I.

H. D. G. C. L. DUNBAR.

BALANCE!) SLIDE VALVE.

(Applutinn 81nd Hay 1, 1901.) (un loden.) 2 sheets-sheet 2.

l l UNITED STATES PATENT OFFICE.

HENRY D. DUNBAR, OF NORTH HARTLAND, VERMONT, AND CHARLES L. DUNBAR, OFLEBANON, NEW HAMPSHIRE.

BALANCED SLIDE-VALVE.

SPECIFICATION forming part of Letters Patent N o. 682,921, da'tedSeptember 17, 1901.

Application filed May 1, 1901.

To all whom it may concern:

Beit known that we, HENRY D. DUNBAR, of North Hartland, Windsor county,Vermont, and CHARLES L. DUNBAE, of Lebanon, Grafton county, NewHampshire, have Vinvented certain Improvements in Balanced Slide-Valves, of which the following is a specification.

The object of our invention is to provide abalanced slide-valve ofsimple construction which will permit free iniiow of steam to thecylinder and unobstructed exhaust therefrom, will be properly packedagainst leakage of steam, can be readily fitted to existingvalve-chests, Will permit free escape of water from the cylinder, andwill provide for the relief of vacuum when the engine is running withthe steam out olf.

ln the accompanying drawings, Figure l is a longitudinal section of abalanced slidevalve constructed in accordance with our invention,illustrating the valve at one extreme of its movement. Fig. 2 is atransverse section on the line a a, Fig. 1. Fig. 3 is a topv view of thevalve, and Fig. 4 is an inverted View of the back plate or shield.

1 represents the ported face of the valve chest; 2, the combinedinduction and eduction passage leading to one end of the cylinder; 3,.the induction and eduction passage leading to the opposite end ofthecylinder, and 4 the exhaust-passage. The valve is of the gridirontype and'has extending through it from top to bottom three passages 5,6, and 7, this valve working in the space between the ported valve-seat1 and a back plate 9, which is rigidly seated upon the valve-seat andconfined in position by suitable meansas, for instance, by screwspassing through the valve-chest cap or cover, so that it is maintainedat a predetermined distance from the' valve-seat 1. The valve isembraced by the usual yoke 10, whichis connected to the valve-operatingrod, and leakage through the valve is prevented by longitudinalpackingstrips locatedat the back of the valve and bearing against theback plate 9. These strips comprise the longitudinal strips 11 at thesides of the valve and transverse strips 12, 13, 14, and 15, the` strips12 and 13 being near the ends of the valve and the strips 14 Serial No.58,273. No model.)

and 15 being interposed between the passages 5 and 6 and 5 and 7,respectively. YThe side packing-strips 11 are deeper than the grooveswhich receive 'the transverse strips 14 and 15 and also by preferencebear the same relation to the grooves which receive the strips 12 and13, and thereby prevent any leakage of steam into said grooves at theends, and the chamber in which each ofthe packing-strips is fitted issomewhat deeper than the strip itself, so that steam can gain access tothe space behind the strip in order to press the same rearwardly againstthe back plate 9, the passages in the side and end strips for thispurpose being preferably in the form of shallow grooves formed in theouter sides of the strips, as shown, for instance, at 16 in Fig. 3, andthe passages for conveying steam to the chambers containing the innerstrips 14 and 15 being in the form of openings 17 of contracted diametercommunicating, re-

spectively, with the spaces 6 and 7, as shown in Fig. 1. Each of thestrips may also be acted upon by a spring or springs deposited in thebase of the groove which contains said stripr The back plate 9 has acentral transverse chamber 19, closed at the ends and which may also beclosed at the top, although it is preferable to extend it through to theback of the plate 9 and there close it by a longitudinal bar 20,normally held down upon the top of the plate 9 by the pressure of steamin the chest, but when the engine is running without steam being liftedby means of springs 21 at the opposite ends to an extent limited by itscontact with the heads of studbolts 22, whereby the opposite ends of thebar are guided, the bar thus acting as a vacuum- -reliel valve for thecylinder of the engine when running under these conditions. Otherpassages 23 and 24 are formed through the back plate 9, one in advanceof the passage 19 and the other in the rear of the same, and thesepassages are normally closed by valve-bars 25, mounted and actuated in amanner simil lar to the bar 20, these valve-bars 25 serving to permitescape of water from the cylinder into the chest in order to preventaccident due to the starting of the engine when there is an undueaccumulation of water in the cylinder. The passages 19, 23, and 24 beingof large ICO area provide for quick relief, and the bars 20 and 25constitute simple forms of valve which can be readily retained in placeupon the plate 9 and which are not likely to get out of order in use,thereby overcoming the objection to the use of ordinary valves or othersupplementary parts within the valve-chest of the engine, where theyareinaocessible during the running of the engine. The passage 19 iscrossed at suitable intervals by bridge-bars 26, which provide a bearingfor the packing-strips 14 and 15 as the valve reciprocates, and the endsof the plate 9 have projecting iingers 27 in order to provide a likebearing for the end strips 12 and 13.

In the operation of the valve steam enters the chamber 6 or 7 of thevalve as soon as the corresponding end bar of the valve has movedoutwardly beyond the end of the valve-seat and back plate, steamentering the chamber both at top and bottom, so that a large area ofopening is available for the iniiow, thereby providing for a quick entryof steam into the cylinder. There is also a double flow into theexhaust-passage-namely, the direct flow from the passage 2 or 3 into thepassage 4 and an indirect iiow through the passage 19 of the back plateand through the central passage 5 of the Valvewhereby free andunobstructed escape of the steam from the cylinder is also insured. Theuse of the back plate 9 insures the proper balancing of the valve, sothat the latter can be operated with the minimum of frictionalresistance, this quality, combined with the provision for effecting freeilow of steam into and from the cylinder, rendering the valve especiallyavailable for engines in which high speed is desirable.

In order to facilitate the fitting of the back plate into its properposition, we provide the depending side portions ot the plate withinwardly-projecting lugs 29 at the lower corners, these lugs overlappingthe ends of the valve-seat, as shown in Fig. 1.

As the steam enters the chambers 6 and 7 of the valve on the inside ofthe end bars of the same, the yoke 10 oers no obstruction to the freeiiow of the steam as it does when the steam has to enter the port of thevalve-seat around the outer edge of the valve. This feature aids in thequick iow of steam into the cylinder, and it may be employed in a valvetaking steam at the top or bottom or at both points, as shown.

Having thus described our invention, we claim and desire to secure byLetters Patent- 1. The combination of the ported valveseat, the backplate rigidly mounted in respect thereto and having a central passagetherein, the valve having a central passage communicating with theexhaust-port and with said central passage of the back plate and neareach end a passage communicating with the corresponding induction-portof the 'eeaeai valve-seat, said latter passage as the valve isreciprocated being opened to the steam-chest at one end of the travel ofthe valve, and to the exhaust-port and back-plate passage at the otherend of the travel oi' the valve, substantially as specified.

2. The 4combination of the ported valveseat and the back plate rigidlymounted in respect thereto and having a central chamber therein with thevalve having a central passage and a passage near each end, the centralpassage being always in communication with the exhaust-port and with thechamber in the back plate, and each end passage being in communicationwith the corresponding ind notion-port of the valve-seat and as thevalve is reciprocated being opened alternately to the steam-chest at topand bottom and to the back-plate chamber and exhaust-port at top and'bottom respectively, substantially as specified.

3. The combination of the ported valveseat and the back plate rigidlymounted in respect thereto, with the valve having near each end apassage communicating with the corresponding induction-port of thevalveseat, said passage being opened alternately to the steam-chest andto the exhaust-port as the valve is reciprocated, and packing-stripslocated on the back of the valve and bearing against the back plate,saidpacking-strips being located respectively at the sides and ends of thevalve, substantially as specified.

4. The combination of the ported valve` seat, the back plate rigidlymounted in respect thereto and having a central passage, the valvelocated between the valve-seat and back plate and having a centralchamber,- and a chamber between said central chamber and each end of thevalve and packing-strips on the back of the valve for bearing againstthe back plate, said packing-strips comprising longitudinal sidepacking-strips, trans-4 verse end packing-strips, and intermediatetransverse packing-strips between the end chambers and the centralchamber of the valve, substantially as specified.

5. The combination ot' the ported valveseat, the back plate rigidlymounted in respect thereto, the valve moving between the valve-seat andback plate and having a central passage, and opposite end passages eX-tending through it from front to back, and packing-strips on the back ofthe valve and bearing against the back plate, said strips comprisinglongitudinal side strips and transverse strips located between thecentral passage and the end passages of the valve, substantially asspecified.

6. The combination of the ported valveseat, the back plate rigidlymounted in respcct thereto, the valve moving between the valve-seat andback plate and having passages extending therethrough, and packingstripson the back of the valve bearing against the back plate,saidpacking-strips comprising Idd both longitudinal and transverse strips,the longitudinal strips being deeper than the transverse strips,substantially as specified.

7. The combination of the ported valveseat, the back plate rigidlymounted in respect thereto, and the valve moving between the valve-seatand back plate and having passages extending through the saine,areliefpassage extending through the back plate, and a iiat bar normallyresting upon the back of the plate and guided at each end so as to .erveas a relief-valve, substantially as speci- 8. The combination of theported valveseat, the back plate rigidly mounted in respect thereto andhaving projecting ngers at each end, and the valve moving between thevalve-seat and back plate and having passages extending through it, andpackingstrips mounted on the back of the valve and bearing against theback plate or its projecting fingers as the valve is reoiprocated,substantially as specified.

9. The combination of the ported valveseat, the Valve and the back platehaving depending side portions resting upon the valveseat, andinwardly-projecting end lugs bearing against the ends of the valve-seat,substantially as specified.

In testimony whereof we have signed our names to this specification inthe presence of two subscribing witnesses.

Witnesses:

F. E. BECHTOLD, Jos. H. KLEIN.

